1. Field of the Invention
The present invention relates to locking devices for locking sheets or films with respect to fastening channels.
2. Prior Art
My U.S. Pat. No. 3,987,835 illustrates a type of fastener that is utilized for fastening sheets or continuous films to channels which in turn are attached to a structure to be covered. In certain instances where the tension in the material is relatively low, and where the sheet being held is relatively stiff, such as in a relatively stiff plastic film, the detent and bar will not rigidly interlock, and the fastener will permit the film to gradually work around the fastening bar and ultimately be released. U.S. Pat. No. 3,987,835 illustrates fasteners which work well in most applications, and the present device constitutes an improvement over that patent as well as my own prior U.S. Pat. No. 3,805,873.
Additionally, U.S. Pat. No. 3,893,212 illustrates a device for making a fastener for plastic film or the like which utilizes a plastic channel with a plastic insert strip, and a similar device to this patent is shown in U.S. Pat. No. 3,999,258.
It should be noted that the device shown in FIGS. 1 through 3 of this continuation-in-part application, and which device was described in application Ser. No. 792,660 mentioned above, has been in public use and on sale more than one year prior to the filing of this continuation-in-part application.